Diffusion tensor imaging (DTI) is a new MR imaging modality that has the unique capability to reveal the anatomy of white matter tracts. This technology offers us exciting new research opportunities. For example, if there is a volume change in the white matter due to development, aging, or pathological conditions, conventional T1 or T2-weighted images could not pinpoint the white matter structures responsible for the change. DTI has the potential to relate these changes to specific white matter tracts. In the past, most of our efforts were focused on the understanding of the white matter anatomy revealed by DTI and developing imaging analysis methods. In the last 4.5 years of our HBP (Human Brain Project) study, we accomplished four major goals. First, we established a high-quality DTI database of approximately 60 normal adult subjects (previous Aim 1). This database is currently available on our website and 316 sites have been registered to use the data. Second, we published a comprehensive atlas of human brain white matter based on DTI (previous overall goal). Third, we performed one of the first attempts to quantify white matter anatomy using population-averaged statistical approaches (previous Aim 2 and 3). Fourth, we developed visualization software, DtiSDView, which is now integrated into a more comprehensive DTI software package, called DtiStudio, and has 1,097 registered users (previous Aim 4). In this proposal, we will extend these past efforts under the same mission: "To contribute to the progress of this new and exciting research field of human white matter anatomy using DTI." Our new aims are as follows;Aim 1: Elaboration of the single-subject white matter atlas: We will create a white matter atlas in Talairach coordinates for educational use and for quantitative white matter anatomy analysis. Aim 2: Creation of statistical atlas of human white matter: Based on the normal adult database, white matter statistical atlases will be developed. We will investigate reproducible structures of the white matter and use them for brain registration studies. Aim 3: Acquisition and analyses of DTI data of normal aging population: In this aim, we will expand our effort to middle age and aging population to study normal aging process of the white matter.